The invention is based on a pressure valve for controlling fluid flow.
In one such pressure valve, known from German Patent Disclosure DE 42 40 302 A1, and disposed in a supply line between a pump work chamber and an injection site, a valve closing member is lifted from its valve seat counter to the force of a spring, causing the pressure valve to open, as a result of a medium which is at high pressure and is supplied to the pressure valve from the pump work chamber via the supply line. At the end of the high-pressure supply, the pressure valve closing member returns to its seat. At the same time, an injection valve at the injection site closes, so that in the enclosed volume between the pressure valve and the injection valve, pressure waves move back and forth and are capable of re-opening the injection valve. To prevent this, a check valve, guided with its closing member in the pressure valve closing member, ia disposed in the interior of the pressure valve closing member, and by way of it the pressure level in the supply line can be reduced, even after the closure of the pressure valve closing member, to a head pressure that is determined by the prestressing of the restoring spring of the check valve.
In the known pressure valve, the check valve is fixedly disposed relative to the pressure valve closing member, and there is a second through conduit in the pressure valve closing member, by way of which the returning medium can be diverted into the pump work chamber.
The known pressure valve has the disadvantage that because of this arrangement, not only is one restoring spring provided for the pressure valve closing member, which presses the pressure valve closing member into the valve seat of the valve body so that the first through conduit is closed from the pump work chamber to the injection valve, but a further restoring spring is also provided in the pressure valve closing member, which keeps the check valve in a closed position and as needed enables a return flow of the medium (after the injection feed pump stops). This makes for a complicated and expensive arrangement for a pressure valve.
The known pressure valve has the further disadvantage that because of the design and disposition of the pressure valve with two restoring springs in the pressure valve, large-volume portions of the through conduit are formed, so that a large idle volume is stored in the pressure valve. On the one hand, this makes it more difficult to build up pressure at the onset of fuel supply, and at the same time increased energy is needed for generating the high pressure.